Ever heard of a conscientious chimp? An extroverted ape? New research suggests that chimpanzees, man's closest living relatives, have personality traits quite similar to their human cousins.

The study, conducted by researchers at Georgia State University, found that chimpanzees not only possess many of the same personality traits as humans — from agreeableness to extroversion — these traits are structured almost identically in both humans and chimps.

"Our work demonstrates the promise of using chimpanzee models to investigate the neurobiology of personality processes," said Robert Latzman, assistant professor of psychology at Georgia State University, who led the research team. "We know that these processes are associated with a variety of emotional health outcomes. We're excited to continue investigating the links."

To analyze chimp personalities, researchers used a common tool called the Chimpanzee Personality Questionnaire. Think of it as a Myers-Briggs test for chimps. Caregivers are asked to rate chimps in 43 categories based on their observations of each animal's daily behavior. Is the chimp excitable? Does it demonstrate impulsive tendencies? Is it playful or timid? [8 Humanlike Behaviors of Primates]

Researchers analyzed 174 of these completed questionnaires from chimp caregivers at the Yerkes National Primate Center at Emory University. The researchers wanted to find out which traits tend to go together in chimps to form more fundamental, overarching traits, called meta-traits.

These meta-traits were found to be the most fundamental personality traits for chimpanzees. Unlike humans, who are typically categorized into five main personality types, chimps generally fall into one of two categories: they're either dominant "Alpha" types or more playful and sociable "Beta" types.

However, the researchers found that being an Alpha or a Beta usually implies that a chimp possesses certain additional personality traits. In their study, the researchers broke down the meta-traits into smaller traits. And it's those smaller traits, they found that closely resemble the five main personality traits of humans: openness, conscientiousness, extraversion, agreeableness and neuroticism. Chimps also tend to exhibit a similar mix of traits — dominance, conscientiousness, extroversion, agreeableness and intellect.

So what accounts for this striking parallel between humans and chimps? Researchers believe it has to do with the species' similar neurobiology, or the prevalence of certain hormones in the brain.

The researchers found that chimpanzee personality traits correlate with the function of a hormone called vasopressin. In humans, vasopressin is known to be involved in regulating both feelings of aggression and feelings of love and generosity.

In chimps, vasopressin was found to contribute to the prevalence of certain personality traits. Male chimps born with a common variant in the genes that control vasopressin were found to be more dominant and disinhibited, while females with this genetic variation tended to be less dominate and more inhibited.

The new research is detailed online on April 21 in the journal PLOS ONE.